Survey Shows Number Of Christians In U.S. Is Declining

The number of Americans who call themselves Christians is on the decline and a growing number of people say they aren't affiliated with any church at all. A new survey by the Pew Research Center suggests America's religious identity is changing. Here to parse the numbers, NPR's new religion and belief correspondent, Tom Gjelten.

Welcome, Tom.

TOM GJELTEN, BYLINE: Hi Audie.

CORNISH: So to begin, "Losing Faith In America" is the headline from Christianity Today. It's certainly attention-grabbing. But how big a shift are we really talking about here?

GJELTEN: Well, Audie, 7 in 10 Americans still identify with Christianity, so that's a vast majority. But in 2007, it was about 8 in 10 and the Pew researchers say that's a big enough jump to be significant. The U.S. is still more religious than Europe, for example. There are more Christians in the United States than in any other country, but there clearly is a trend here. And on the other side, as you say, we're seeing what Pew calls the rise of the nones. Nearly 23 percent of all U.S. adults now say they have no religious affiliation. In 2007, it was just 16 percent.

CORNISH: Any clues as to what's going on, why the decline?

GJELTEN: We know that as people become wealthier and more educated, they tend to become more secular. That could be one thing that's going on. We also know that people are not doing things in groups as much, they're living more independently, doing more things alone. That would definitely hurt something like church membership because people just don't associate as much. Something else, Audie, to emphasize here in terms of what we're seeing is what Pew calls generational replacement. The millennial generation is much less likely to be affiliated religiously then baby boomers, for example. Pew says 35 percent of the millennial generation are unaffiliated religiously. So as these young people enter adulthood, we're going to see lower and lower levels of religious affiliation.

CORNISH: And it sounds like these declines were across the board. I mean, are there any particular denominations that saw maybe a sharper decline than others?

GJELTEN: Well, the biggest declines are in the mainline denominations - mainline Protestants and Roman Catholics. Fewer, smaller declines for example, in the evangelical Protestants and in the historically black Protestant denominations. One explanation for that may be that we see less intermarriage in those groups. When people of different faith traditions marry, there could be some loss of religiosity. One thing Pew identifies is a high degree of what they call religious switching, people growing up in one faith and then switching to another. Thirty-four percent of American adults have a different religious identity now then the one they had in childhood. One out of 5 people raised as a Christian now say they are no longer Christian. So that could be due in part to intermarriage and therefore those denominations that have less intermarriage are more likely to be holding steady.

CORNISH: So Christianity's numbers are on the decline here in the U.S. What about other religions?

GJELTEN: Well, Judaism and Buddhism are essentially stable, Islam and Hinduism rising slightly. That may have to do with population factors, immigration and higher fertility in those groups. We are also seeing a increase in the number of - within the group of people who say they are unaffiliated, we're seeing an increase in the number of people who say they are atheists or agnostics. In the past, some of the people who were unaffiliated religiously said that religion in general was still important. We've seen a decline in that, a growth in atheists and agnostics. So definitely something's going on here.